We have benched these to death on Overclock.net. The Athlon 860K always ends up with higher minimum FPS in games (and higher overall) than the FX-6300. It seems to be due to the cache misses and latency issues found in all BD/PD chips.
The only thing the extra 2 piledriver cores are good for is streaming (like recording while you play). But in that case you should be getting the FX-8310 which is still cheaper (often $89 at Tiger Direct or Microcenter) and stronger than the FX-6300 for streaming.